Electric primers for projectiles



y 1963 LOUIS-DAVID PASCHOUD 3,09

ELECTRIC PRIMERS FOR PROJECTILES Filed Oct. 24, 1960 INVENTOR LOU/519A V/D PASCHOL/D ATTOFPN Y United States Patent Ofitice 3,090,308 Patented May 21, 1963 3,090,308 ELEQTC PRTMERS FGR PROJEQTXLES Louis-David Paschoud, Lausanne, Switzerland, assignor to Brevets Aero-Mecaniques A., Geneva, Switzerland,

a corporation of Switzerland Filed Get. 24, 1960, Ser. No. 64,466 Claims priority, application Switzerland Oct. 28, 1959 6 Claims. (Cl. 102-48) Electric primers for projectiles are already known, comprising two electrodes connected one to the other by a conducting bridge or layer disposed on an insulating support.

By reason of the technical progress realised, it has been possible to construct primers of this type in which a relatively low voltage, for example of the order of 40 volts, is sutficient to cause a spark to jump over to the conducting bridge. By reason of this lowering of the ignition voltage, it is to be feared that the primer may cause the ignition of the detonating charge in an untimely manner.

The present invention has for its object to remedy this disadvantage. It has for its object an electric primer of the type referred to, characterised in that the conducting bridge is covered with a protective layer on its face opposite that which contacts the insulating support.

One form of construction of a primer, subject of the invention, is shown diagrammatically and by way of example in the accompanying drawing.

This primer is constituted by a metal part 1 of cylindrical shape, having a central hole 2 and an axial projecting finger or stud 3. This part 1 is located in a metallic sleeve 4 with the interposition of an insulating ring 5 ensuring its centering relatively to this sleeve. An insulating mass 6 fills the free space between the part 1 and the sleeve 4 and on its upper face carries a thin layer 7 of metal, deposited in colloidal form, constituting a conducting bridge.

The part 1 constitutes a first electrode in contact with the layer 7, which itself is in contact with a second electrode constituted by the parts 8, 9 and 4.

The part 9 constitutes a shell which surrounds the sleeve 4, and also the part 8'. This latter is of cylindrical shape and comprises a base 10 having an orifice 11 located opposite the finger 3. The edge of this orifice 11 is in electrical contact with the conducting bridge.

It will be seen that the second electrode has a portion in the general shape *of a pot which surrounds the first electrode 1 with the interposition of an insulating substance. The wall of this pot is constituted by the sleeve 4 and the bottom of this by the base 10 of the part 8. This latter defines a chamber adapted to contain a detonating charge 13. In order to prevent the primer from functioning when a low voltage is applied between the two electrodes, the active part of the conducting bridge, which is located opposite the orifice 11, is covered by a protective layer 12 on its face opposite that which touches the insulating mass 6.

Preferably, this layer 12 is electrically insulating. It may, for example, be constituted by a varnish, by paper or even by fabric, particularly a silk fabric. In .this manner, the ignition of the primer can only be obtained when the spark between the finger 3 and the conducting bridge, has suflicient energy for destroying the protective layer 12.

In selection of the material and the thickness of the layer 12, it is possible to fix the minimum level of energy necessary for causing the functioning of the primer.

I claim:

1. An electric primer for a projectile comprising in combination, first and second electrodes, the first electrode comprising a metallic member of generally cylindrical shape having a centrally disposed opening at one end and a stud projecting from its opposite end, the second electrode comprising a metallic shell, a pair of metallic sleeves within said shell and disposed one above the other, each of said sleeves in contact with said shell, the uppermost sleeve containing a detonating charge and having an opening in its bottom wall opposite the stud of said first electrode, the lowermost sleeve enclosing said first electrode and insulating means therebetween, a metallic conducting bridge supported on the upper surface of said insulating means and in contact with each of said electrodes, and a layer of protective material on said conducting bridge on the face thereof opposite that Which contacts said insulating means, said protective material sealing the opening in the bottom wall of the uppermost sleeve to thereby separate the detonating charge contained in said sleeve from the stud of the first electrode and the insulating bridge.

2. A primer according to claim 1, wherein said protective layer is electrically insulative.

3. A primer according to claim 1, where said protective layer comprises a varnish.

4. A primer according to claim 1, where said protective layer comprises paper.

5. A primer according to claim 1, wherein said protective layer comprises a fabric.

6. An electrical primer for a projectile comprising, first and second cylindrical electrodes, said second electrode including an internal sleeve provided with a base, said base having an orifice, said first electrode disposed within and spaced from said second electrode, an insulating mass between said electrodes, said sleeve of said second electrode containing an explosive charge to be ignited by a spark jumping between said electrodes, a part of said first electrode emerging from said insulating mass adjacent said orifice in said base, a single metallic deposit in colloidal form overlying said insulating mass and connecting said first and second electrodes adjacent said orifice in said base, a single protective layer of electrically insulative material disposed upon said metallic deposit opposite said orifice, said protective layer overlying said metallic deposit and being contiguous therewith, said protective layer completely isolating said explosive charge from said metallic deposit and said first electrode, whereby, a spark of suificient intensity to properly ingite said explosive charge will destroy said protective layer and contact said charge to ignite the same.

References Cited in the file of this patent 

6. AN ELECTRICAL PRIMER FOR A PROJECTILE COMPRISING, FIRST AND SECOND CYLINDRICAL ELECTRODES, SAID SECOND ELECTRODE INCLUDING AN INTERNAL SLEEVE PROVIDED WITH A BASE, SAID BASE HAVING AN ORIFICE, SAID FIRST ELECTRODE DISPOSED WITHIN AND SPACED FROM SAID SECOND ELECTRODE, AN INSULATING MEANS BETWEEN AID ELECTRODES, SAID SLEEVE OF SAID SECOND ELECTRODE CONTAINING AN EXPLOSIVE CHARGE TO BE IGNITED BY A SPARK JUMPING BETWEEN AID ELECTRODES, A PART OF SAID FIRST ELECTRODE EMERGING FROM SID INSULATING MASS ADJACENT SAID ORIFICE IN SAID BASE, A SINGLE METALLIC DEPOSIT IN COLLOIDAL FROM OVERLYING SAID INSULATING MASS AND CONNECTING SAID FIRST AND SECOND ELECTRODES ADJACENT 